WASHINGTON — The Air Force said on Wednesday that 34 officers responsible for launching the nation’s nuclear missiles had been suspended, and their security clearances revoked, for cheating on monthly proficiency tests that assess their knowledge of how to operate the warheads.

At a news conference, Deborah Lee James, the secretary of the Air Force, said the officers, at Malmstrom Air Force Base in Montana, either knew about or took part in texting answers to the routine monthly tests.

Eleven Air Force officers — including two accused in the Malmstrom cheating scandal, as well as one other nuclear missile officer — have also been the focus of suspicion in an illegal drugs investigation, defense officials said.

Although the Air Force has been plagued in recent years by scandals, the current revelations are particularly alarming because they involve America’s nuclear arsenal, where errors could be catastrophic.

“There’s no making this better,” said Kathleen Hicks, a former top defense official in the Obama administration now with the Center for Strategic and International Studies. She called any potential security lapse in the country’s nuclear arsenal as “worrisome. Period. Full Stop.”

Defense officials insisted that the nation’s nuclear arsenal remained safe.

“This is not about the compromise of nuclear weapons,” said Gen. Mark A. Welsh III, the Air Force chief of staff. He called the revelations a “compromise of the integrity of some of our airmen” and said the Air Force “will not accept or allow that type of behavior.”

He characterized the Malmstrom case as the largest cheating episode he had come across among missile launch officers.

Defense experts say that the end of the Cold War and the elevation of counterterrorism in the American military has led to low morale among the men and women, known as missileers, who live and work within a hair trigger of the country’s 450 nuclear missiles. The missileers have increasingly come to view their mission as a backwater, with little chance of advancement to the top ranks of the Air Force.

Bruce G. Blair, a former Minuteman missile launch control officer, said missile officers routinely cheated, in part because the Air Force required them to score 100 percent on the proficiency tests. “Perfection is demanded of all of these crew members, and it’s an impossible standard,” Mr. Blair said.

The Air Force cheating and drug scandals come at a time when a large number of senior officers in other branches of the military have been investigated, penalized or fired in connection with allegations of sexual improprieties, sexual violence, financial mismanagement or poor judgment.

But Air Force nuclear missile officers have had particular problems. Last month, an Air Force inquiry revealed that the general who oversaw some of the nation’s nuclear weapons was dismissed for drunken antics during an official trip to Moscow last summer.

The officer, Maj. Gen. Michael J. Carey, was removed as commander of the 20th Air Force, which maintains and operates intercontinental ballistic missiles, after being accused of drinking heavily, insulting his guests, consorting with someone identified as the “cigar shop lady,” and slurring his speech while weaving in Red Square, “pouting and stumbling.”

Last May the Air Force disclosed that it removed 17 officers assigned to stand watch over nuclear-tipped Minuteman missiles after finding safety violations, potential violations in protecting codes and attitude problems.

And last November, The Associated Press reported that Air Force officers with nuclear launch authority had twice been caught napping with the blast door open. That is a violation of security regulations meant to prevent a terrorist or intruder from entering the underground command post and compromising secret launch codes.

The Pentagon disclosed the original drug inquiry last week, but officials have declined to go into details on the investigation, which is continuing, other than to say that the officers are suspected of possessing recreational drugs.

Senator Mark Udall, Democrat of Colorado and chairman of the Senate subcommittee that oversees the nuclear arsenal, said Wednesday of the cheating scandal that “there is simply no room in our Air Force, and certainly in our nuclear enterprise, for this type of misconduct.”

Ms. James said she would travel next week to missile launch sites to discuss ways to prevent future problems. She said that 600 missile crew members across the Air Force, including all of the 190 officers at Malmstrom, would retake the proficiency test by Thursday.

General Welsh said the time frame for the cheating alleged to have occurred was last August and September.

As for the reports in November of crews sleeping with the blast door open, Mr. Blair said that back when he was a missileer, “everyone slept with the blast door open.”

Correction:

An article on Thursday about a cheating scandal involving 34 officers at Malmstrom Air Force Base who oversee the nation’s nuclear warheads misidentified, in some copies, the state in which the base is located. It is in Montana, not in North Dakota.

A version of this article appears in print on , on Page A14 of the New York edition with the headline: Cheating Accusations Among Officers Overseeing Nuclear Arms. Order Reprints | Today’s Paper | Subscribe